DewPro MMY245
Installation and Operation Manual
GE General Eastern
20
The mechanical connections are made to the same sample as the MMY 3 transmitter with a short length of
small diameter tubing. The sample from the transmitter travels the short distance quickly and the two
sensors read virtually the same sample at almost the same time. As soon as the mechanical connection is
made, initiate the gas sample flow to the MMY 245 to begin drying down the tubing and fittings.
The digital link between the two units is through a two-wire RS-485 connection using Cable P/N
63004006. The cable connection at the MMY 245 is made with a bayonet connector on the front of the
portable unit. The cable connection at the MMY 3 is made with a bayonet connector on the conduit housing
where Cable P/N 63004005 has been installed. Power to operate the MMY 3 transmitter continues to come
from the loop and its internal batteries supply power for the MMY 245.
Warning!
The initial installation of Cable P/N 63004005 will require opening the transmitter
enclosure. If the transmitter is located in a hazardous area, all electrical connections
must be performed in accordance with local electrical codes. This may mean that
the transmitter be removed to a safe area where the validation can be performed on
a similar sample gas.
Warning!
Do not connect the MMY 245 to an external power source during the validation
process. This could damage the unit.
After mechanical and electrical connections are made, the MMY 245 should be powered up and the handle
moved into the vertical (measure) position to display the reading and begin equilibrating the sensor to the
sample moisture content. The bar graph is a good indicator of how stable the reading is and should be
monitored to insure the unit is stable (see Figure 3). It is recommended that even after a stable condition is
indicated on the display that the unit is allowed another ten minutes to settle before continuing the
validation procedure.
The two procedures are a single-point validation that simply changes the EEPROM data to move the
intercept of the curve, and the two-point validation that changes the slope and intercept. The single-point
procedure is very brief requiring the sample readings of both devices to be equilibrated and stable. The data
will be automatically be written to the EEPROM of the MMY 3 series transmitter almost immediately once
the single-point procedure has been initiated. Upon initiation of the two-point procedure, the instrument
will automatically stop and wait after capturing the low moisture value. This is to allow the technician to
change the sample conditions for both the transmitter and the MMY 245 to a higher moisture content. Once
this has been ‘seen’ by the instrument, it will continue by attempting to capture the higher moisture value
for both units for comparison. After this point has been captured, the data will be automatically be written
to the EEPROM of the MMY 3 series transmitter.
4.1 Optimum Validation Practice
For optimum performance of the field validation technique, the MMY 245 should be factory calibrated
within 4 months of validating MMY 3 series transmitters. This will insure that the freshest possible data is
used for comparison during the validation process.
For the single point calibration the process is very quick. The reason is that the single point calibration
assumes that both the transmitter and the MMY 245 are already measuring and equilibrated to the same
value in the same stream or sample. The transmitter reading is then checked against that of the MMY 245
and the EEPROM data in the on-line transmitter is programmed almost immediately. If either the
transmitter or the MMY 245 are not equilibrated, then the validation of the on-line transmitter will not be
reliable. To insure both devices have reached equilibrium, monitor the output of the transmitter for a steady
